This invention relates to improvements in method and apparatus for positioning a point at one elevation in predetermined relation to a known point at a different elevation. More particularly the invention is intended to be utilized primarily in the building construction industry as an aid in properly positioning and aligning electrical fixtures, heating and air conditioning outlets, structural frameworks, walls, decorative moldings, etc. The invention can be used to provide direct vertical alignment of points or offset relationships of predetermined magnitude.
In vertical positioning devices of the type known to the art and shown for example in Martinez U.S. Pat. No. 3,407,509 and O'Connell et al U.S. Pat. No. 3,162,957, means are provided for locating a point on a ceiling vertically above a known point on the floor. The utility of such devices is severely limited, however, by their lack of capability for performing the reverse function, i.e. locating a point on the floor in relation to some known overhead point. In addition such devices are unable to relate to vertical surfaces, such as that of a ledge of molding, or of providing offsets of predetermined variable magnitude between upper and lower points.
In order to accomplish any of these latter functions, all of which are commonly required in construction work, two or three workmen are normally needed, one standing on a ladder and holding a plumb line at a desired overhead location while a second man on the floor monitors the position of the plumb bob. A third man holding the ladder for the first workman is also usually required. Each such separate procedure for positioning a desired point in relation to a known point or vertical surface is quite time consuming, and the great number of such procedures required for any particular construction job, coupled with the fact that two or three men must take part in each procedure, adds markedly to the required man hours and resultant cost of the job.
Accordingly a great need exists in the building and construction industry for a more versatile device and method for positioning points at one elevation in aligned or offset vertical relation with known points or vertical faces at a different elevation, particularly where the known points are located at overhead elevations, such apparatus and method being such that points may be positioned swiftly and accurately by one man working alone from a location on the ground or floor.